1. Field of the Invention
The present invention relates to cleaning compositions and, more particularly, to strong acid-based cleaning compositions. Specifically, the present invention relates to a composition for cleaning copper and copper alloys, such as brass and bronze, which composition has a pH value of less than 1.0 yet is nonreactive and nonirritating to human skin tissue.
2. Description of the Prior Art
Numerous compositions and processes have been employed in the past for the purpose of brightening and cleaning deposits, residue and impurities from copper and copper alloys such as brass and bronze. Various abrasive techniques have also been used in the past, such as scrubbing, scouring, sand blasting and the like, for the purpose of removing such materials. In addition, chemical compositions ranging from degreasers and detergents to extremely corrosive acid baths and washes as well as caustic chemicals, which are difficult and messy to apply, have been used for various copper and copper alloy cleaning applications.
Examples of acidic compositions which have been utilized for a wide variety of cleaning applications include U.S. Pat. Nos. 4,675,120, 3,514,407, 3,630,933, 4,116,713, 4,181,622, 4,199,469, and 4,250,048. While many of these referenced patents are not specifically designed for cleaning copper and copper alloys, they do disclose acid-based compositions for the purposes of cleaning a wide variety of different types of surfaces. One unfortunate and significant disadvantage of many of these acid-based cleaning compositions is that while they are effective cleaning agents, they can be extremely corrosive and highly reactive with human skin tissue as well as other compositions having relatively low oxidative states. U.S. Pat. No. 4,477,364 discloses an acidic glass cleaning composition which has a low pH value for cleaning yet is relatively innocuous to skin tissue. However, this particular disclosure is directed only to the specific challenges relating to the cleaning of glass surfaces and is so limited thereto.
Abrasive cleaning methods tend to be very destructive and physically tiresome, and the abrasion process tends to scratch the metal surface being cleaned, thereby removing its natural luster. Moreover, abrasive cleaning is only temporarily effective and tends to be inconsistent in removing excess material from the surface being cleaned. It also tends to remove excess metal in some areas while not enough in others thereby creating weak spots and eroding different copper surface materials beyond acceptable tolerances. While soaps and degreasing solutions eliminate oil and grease build-up, they generally have negligible effect on oxides and surface discoloration. Moreover, acid-based cleaning solutions tend to react with these metals, and the pH values of acid-based cleaning solutions must be carefully controlled to avoid excessive corrosion and damage to the metal surfaces. The pH value of acid-based cleaning solutions must be low enough to provide the desired oxidation for cleaning, yet it must be sufficiently mild enough to permit ease of handling. Otherwise, strong acid-based solutions require special handling techniques and equipment not readily available to the average household user.
As a result of the above, there is still a need for an effective cleaning solution particularly applicable to copper and copper alloys such as brass and bronze, such cleaners having requirements different from those of cleaning agents for other types of materials, surfaces and applications. Such a cleaning composition need not be abrasive, and should be effective in removing residue, deposits and impurities, non-corrosive to the copper or copper alloy surface being cleaned, and non-reactive with human skin tissue to permit easy and safe use by household or commercial consumers.